1. Technical Field of the Invention
The present invention relates to an imaging apparatus capable of recording an image electronically, and in particular to the imaging apparatus having both an optical zoom function and an electronic zoom function.
2. Related Art
Recently, a digital camera which electronically records an image has been widespread, replacing a film camera. Usually the digital camera has an optical zoom function and an electronic (digital) zoom function. In the optical zoom function, a size of the image imaged on an imaging device such as a CCD (Charge Coupled Device) is optically varied by varying a lens position of an optical system. In the electronic zoom function, magnification of the image is varied by digitally processing an output signal of the imaging device.
In the optical zoom, the size of the image imaged on the CCD is changed by moving a zoom lens, which enlarges and reduces the image. In this case, a recorded image is generated using all the pixels of the image on the CCD. On the other hand, in the electronic zoom, a part region of the image imaged on the CCD is cut out, and processes such as complementation and averaging are applied to the image of the cutout region to generate the recorded image having desired magnification. In this case, the zoom magnification is changed based on the size of the cutout region. An amount of optical information obtained by the CCD is not changed during the electronic zoom, and thus it is generally thought that image quality is degraded when the image is enlarged by the electronic zoom.
In the conventional digital camera, the optical zoom is utilized in region on a wide angle side of the optical zoom, and switched to the electronic zoom when the zoom lens reaches an end on a telephoto side (see JP-A-2000-231149). Thus, large magnification is realized by combination of the optical zoom and the electronic zoom.
Generally, performance of the lens degrades more (shading, chromatic aberration, degradation of resolution, and the like) towards a peripheral portion of the lens. In the conventional zoom method, the optical zoom is performed in the region on the wide angle side, and thus the recorded image is generated using all the pixels (whole region) of the image imaged on the imaging device. That is, the recorded image is generated using the image including the image formed by the region of the lens peripheral portion. As a result, there is a problem that the image quality of the recorded image is degraded by the influence of the performance degradation (shading, chromatic aberration, and degradation of resolution) in the lens peripheral portion.
The invention is directed to the foregoing problem, and has an object to provide an imaging apparatus capable of providing an imaged image of which image quality degradation can be suppressed with no influence of lens performance degradation in the lens peripheral portion during the zoom action.